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LHC refrigerators at 4.5K

To cooldown the LHC superconducting magnets, eight refrigerators of 18 kW @ 4.5 K have been built (4 by Air-Liquide and 4 by Linde). The compressor station is composed of 5 oil lubrificated screw compressors able to compress a total massflow of 1.6 kg/s of helium between 1 bar and 19 bar. The coldbox is composed of 10 Heat Exchangers and 10 turbines.
Each refrigerator cools a 1/8 of the LHC that constitute a coldmass of 4595 tonnes over 3.3km. A refrigerator can provide up to 240 g/s of supercritical helium at 4.5 K and 3 bar to the LHC and 250 g/s between 50 K and 75 K to cooldown thermal screens.

A 4.5K Cold Box for the LHC (Linde)

Schema of 4.5K Cold Box for the LHC (Linde)

One one these refrigerators (compressor station + coldbox) has been modeled using the cryogenic simulator to simulate the dynamic behavior of a such large-scale cryogenic plant. The complete model embeds 4677 equations whereof 392 differential equations.

Simulation Results :

Some simulated variables during a the starting of the compressor station

Some simulated variables during a cooldown of the coldbox alone between 300 K and 4.5 K

TS diagram of the coldbox connected to the LHC obtained in simulation compared to real measurements during steady-state

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Last update: December 2021